The present invention relates to gas discharge panels such as plasma display panels and the like.
Plasma display panels (PDPs) are one of the various types of plasma display apparatuses. Given their relative suitability for thin, large-screen applications, PDPs are currently attracting attention as the possible displays of the future, and 60-inch class models are already available on the market.
FIG. 42 is a partial perspective view showing a main structure of a known surface-discharge AC-type PDP. In FIG. 42, a thickness of the PDP is in the z direction and the panel surface of the PDP lies parallel to the xy plane. The PDP includes a front panel 20 and a back panel 26 arranged so that the main surfaces of each panel face each other.
A front panel glass 21 forms a substrate of front panel 20. Plural pairs of display electrodes 22 and 23 (i.e. scan electrode 22 and sustain electrode 23) extending in the x direction are arranged on a main surface of front panel glass 21 so as to enable a surface discharge to be conducted between the electrodes 22 and 23 in each pair. The electrodes 22 and 23 can be formed, for example, from a mixture of Ag and glass.
Each scan electrode 22 is electrically independent with respect to its power supply. In contrast, each sustain electrode 23 is connected to the same power supply. A dielectric layer 24 and a protective layer 25, both of which are formed from an insulating material, are coated in the stated order over the surface of front panel glass 21 on which the pairs of display electrodes are arranged.
A back panel glass 27 forms a substrate of back panel 26. A plurality of address electrodes 28 extending in the y direction is arranged in a stripe-pattern on a main surface of back panel glass 27, and a predetermined space is provided between adjacent address electrodes. The address electrodes may be formed from a mixture of Ag and glass.
A dielectric layer 29 formed from an insulating material is coated over the surface of back panel glass 27 on which address electrodes 28 are arranged. Barrier ribs 30 are provided between adjacent address electrodes 28 on dielectric layer 29. Phosphor layers 31, 32, and 33 corresponding to the colors red (R), green (G) and blue (B) are formed between adjacent barrier ribs 30, the phosphor layers being formed on the barrier rib walls and over the dielectric layer 29 between adjacent barrier ribs.
Front panel 20 and back panel 26 as described above are arranged to face each other such that address electrodes 28 extend in an orthogonal direction to display electrodes 22 and 23.
Front panel 20 and back panel 26 are sealed together around their respective peripheries using a sealing material such as frit glass, and a vacuum is created within the space enclosed therebetween.
In should be noted that only one of each of electrodes 22, 23 and 28 has been shown in FIG. 42 for ease of description. The known PDP as described here actually includes a plurality of each of these electrodes.
A discharge gas (enclosed gas) that includes Xe is enclosed at a predetermined pressure (approx. 40 kPa to 66.5 kPa in conventional PDPS) within the sealed space between the front and back panels.
A discharge space 38 is thus formed in the space defined between dielectric layer 24 of front panel 20, phosphor layers 31-33 of back panel 26, and adjacent barrier ribs 30 interposed therebetween Furthermore, a plurality of cells (not depicted in FIG. 42) used in image display is provided in discharge space 38, each cell being formed in the region where a single address electrode 28 extends across a single pair of display electrodes 22 and 23. FIG. 43 shows the matrix of the PDP formed by the plural pairs of display electrodes 22, 23 (N line) and the plurality of address electrodes 28 (M columns).
When the PDP is driven, a discharge is initiated between address electrode 28 and either display electrode 22 or 23 in each of the cells. Ultraviolet light (Xe resonance line; wave length approx. 147 nm) having short wavelengths is generated as a result of a discharge that. then occurs between display electrodes 22 and 23 in each pair, the generated ultraviolet light striking phosphor layers 31 to 33 and exciting them to emit visible light. Image display is achieved as a result.
The following is a detailed description of a prior art method for driving the known PDP with reference to FIGS. 44 and 45.
FIG. 44 is a conceptual block diagram showing an image display apparatus (PDP display apparatus) using the known PDP. FIG. 45 shows exemplary drive waveforms applied to each of the electrodes in the PDP.
As shown in FIG. 44, in order to drive the PDP, the PDP display apparatus includes the following elements: a frame memory 10, an output processing circuit 11, an address electrode drive apparatus 12, a sustain electrode drive apparatus 13, and a scan electrode drive apparatus 14. Each of electrodes 22, 23 and 28 are connected to scan electrode drive apparatus 14, sustain electrode drive apparatus 13, and address electrode drive apparatus 12, respectively. Elements 12, 13 and 14 are connected to output processing circuit 11.
When the PDP is driven, image information inputted into the PDP display apparatus from an external source is initially stored in frame memory 10, and then based on timing information, the image information is transferred from frame memory 10 to output processing circuit 11. Then, based on the image information and the timing information, output processing circuit 11 becomes operational. Output processing circuit 11 outputs instructions to the elements 12, 13 and 14, and applies pulse voltages to each of electrodes 22, 23 and 28, thereby conducting the image display.
As shown in FIG. 45, when the PDP is driven, a setup pulse is applied to scan electrodes 22, initializing a wall charge within each of the cells. Next, a scan pulse and a write pulse are applied respectively to scan electrode 22 and sustain electrode 23 positioned at the top of the screen (i.e. in the y direction), thus initiating a write discharge. As a result of the write discharge, wall charge is stored on the surface of dielectric layer 24 in each of the cells corresponding to the electrodes 22 and 23 that have been applied with the pulses.
Continuing on, a scan pulse and a write pulse are then applied respectively to scan electrode 22 and sustain electrode 23 in the line second from the top of the screen, and wall charge is stored on dielectric layer 24 in each of the cells corresponding to the electrodes 22 and 23 in the stated line. One screen of latent image is thus written by repeating this process for all display electrodes 22 and 23 forming the display surface.
Next, a sustain discharge is conducted by grounding address electrodes 28 and applying sustain pulses alternately to scan electrodes 22 and sustain electrodes 23. A discharge is generated in the cells storing wall charge on dielectric layer 24 when the potential of the surface of layer 24 increases above the discharge initiating voltage in the respective cells. The sustain discharge is maintained in the cells applied with the write pulse for the duration that the sustain pulses are applied (i.e. sustain period). Erase pulses, each of short duration, are then applied so as to weaken the discharge and eliminate the wall charge, thereby serving to erase the latent image.
In television image display according to the NTSC standard, one image is composed of 60 fields per second. Primarily, a PDP is only capable of expressing the two states of xe2x80x9conxe2x80x9d and xe2x80x9coff.xe2x80x9d Thus, in order to display the intermediate color gradations, a method is adopted according to which the xe2x80x9conxe2x80x9d periods of each of the colors red (R), green (G) and blue (B) are timeshared and one field is divided into a plurality of subfields. The intermediate color gradations can thus be expressed depending on the combination of xe2x80x9conxe2x80x9d and xe2x80x9coffxe2x80x9d subfields.
The subfield division method used by the known AC PDP and shown in FIG. 46 expresses 256 color gradations. The ratio of sustain pulses applied during the sustain periods in each subfield is layered in a binary scale, an example of which is 1, 2, 4, 8, 16, 32, 64, 128. 256 color gradations can be expressed by varying the combination of these eight bits.
As described above in relation to the method for driving the prior art PDP, display is achieved by a consecutive sequence of setup, write, sustain, and erase periods.
However, in a day and age when any viable reduction in the energy consumption of electrical appliances is greatly valued, much emphasis has naturally been placed on reducing the power requirements of PDPs. In the last few years, an increasing emphasis has been placed on technology that realizes such power reductions, given that the general push toward larger screens and higher definition image display has resulted in recently developed PDPs exhibiting a tendency for increased power consumption. For these reasons, technology that reduces the power consumption of PDPs is most desirable.
However, simply reducing the power consumption of PDPs is not in itself enough, since this will only weaken the discharge occurring between the display electrodes, and cause an insufficient illumination. Therefore, any reductions in power consumption must be accompanied with the ability to achieve a satisfactory display capacity (i.e. a satisfactory luminous efficiency). Since insufficient illumination causes a drop in PDP display capacity, simply reducing the power usage of PDPS is not likely to realize any improvements in luminous efficiency.
Research aimed at improving luminous efficiency is currently being conducted, an example of which includes trying to improve the efficiency at which the phosphors convert ultraviolet light into visible light. However, significant improvements are yet to be realized and further research into this area is still required.
Thus, at this point in time, optimizing the luminous efficiency in gas discharge panels such as PDPs is considered to involved a great many difficulties.
In view of the issues discussed above, an objective of the present invention is to provide a gas discharge panel having a high luminous efficiency and an excellent display capacity.
In order to resolve the above issues, the gas discharge panel of the present invention includes (i) a plurality of cells arranged in a matrix between a pair of opposing substrates, the cells being filled with a discharge gas, and (ii) plural pairs of display electrodes arranged on a surface of one of the substrates so as to extend through the plurality of cells, each pair of display electrodes being composed of a sustain electrode and a scan electrode that define a main discharge gap therebetween. Furthermore, each sustain electrode and scan electrode includes a plurality of line parts that extend in a row direction of the matrix. By adjusting the main discharge gap and a line part gap between adjacent line parts, it is possible to generate a discharge current waveform of the display electrodes that has a single peak when the gas discharge panel is driven.
Specifically, it is preferable for at least one of the scan electrode and the sustain electrode within each cell to be composed of three or more line parts. It is furthermore preferable for a pitch of the line part gaps in each cell to decrease as the distance separating the respective line part gap from the main discharge gap increases.
Discharge current wavelengths having single peaks can be achieved according to this structure, thereby enabling the discharge illumination generated by a single drive pulse to be completed within 1 xcexcs. Also, the fact that the period from when the drive pulse is applied when the discharge current reaches a maximum value (i.e. the discharge delay period) is only short at approximately 0.2 xcexcs, allows the gas discharge panel to be driven at the high speed of a few xcexcs.
Furthermore, the fact that display electrodes 22 and 23 are arranged in lines allows for a reduction in the amount of static electricity arising from the discharge in comparison to when the display electrodes are arranged in bands as per the prior art. Generally, when pairs of display electrodes are arranged in lines, the tendency is for the discharge to disperse, the discharge current waveform to develop multiply peaks, and the discharge initiating voltage to increase, thereby invariably resulting in increased power consumption. However, because the discharge current waveform of the present invention as described above forms a single peak, it is possible to drive the gas discharge panel at a relatively low voltage, thereby suppressing power consumption below existing levels and achieving a favorable luminous efficiency (drive efficiency).
Consequently, the gas discharge panel of the present invention is able to achieve excellent luminous efficiency and high-speed driving by securing a discharge voltage waveform having a single peak while at the same time reducing power consumption through the provision of display electrodes 22 and 23 having a reduced surface area (i.e. line parts 22a-22c, 23a-23c in FIG. 1) in comparison to known display electrodes.
Furthermore, in the present invention, a discharge voltage waveform having an excellent single peak may be achieved by reducing the, pitch of the line part gaps either geometrically or arithmetically.
Also, in regard to the actual construction of the present invention, it is preferable to establish the cell length in the column direction of the matrix to be in a range of 480 xcexcm to 1400 xcexcm, and to satisfy the expression G-60 xcexcmxe2x89xa6Sxe2x89xa6G+20 xcexcm with respect to each cell, where S is the width of an average line part gap in a respective cell, and G is the width of the main discharge gap.
Furthermore, the line parts positioned furthest from the main discharge gap in each cell may be wider than (i) the other line parts in the cell or (ii) an average width of all the line parts in the cell.
In addition, the line parts within each cell may increase in width as the distance separating the respective line part from the main discharge gap increases.
Here, it is preferable to establish the width of the lineparts to satisfy the expression Lavexe2x89xa6Lnxe2x89xa6{0.35Pxe2x88x92(L1+L2+. . . Lnxe2x88x921)} with respect to one of the sustain electrode and scan electrode in each cell, where P is the cell length in the column direction of the matrix, Ln is the width of the line parts positioned furthest from the main discharge gap, Lava is the average width of all of the line parts in the cell, and the sustain electrode or scan electrode includes n line parts.
Also, it is preferable for the resistance value R of the line parts positioned furthest from the main discharge gap within each the cell to be in a range of 0.1 xcexa9xe2x89xa6Rxe2x89xa680 xcexa9.